Center for Embedded Networked Sensing (CENS) Using Cyclops-7 Fluorometer in Monitoring of Algal Blooms

About CENS:
CENS, a NSF Science & Technology Center, is developing Embedded Networked Sensing Systems and applying this revolutionary technology to critical scientific and social applications. Like the Internet, these large-scale, distributed, systems, composed of smart sensors and actuators embedded in the physical world, will eventually infuse the entire world, but at a physical level instead of virtual.

Project Overview:
A specific area in which CENS technology is being applied is the monitoring of harmful algal blooms (HABs). A variety of naturally-occurring and introduced microorganisms adversely impact marine ecosystems and uses of marine resources. They can affect human health, fisheries and even tourism. However, conditions under which HABs develop are not well understood, and methods for detecting microorganisms are too slow and complex for timely intervention. With the development of technology, sensor networks provide a method to monitor the microorganisms in real time and solve the problem. The goal of this project is to deploy large numbers of sensors and robots operating in a semi-autonomous but coordinated fashion in the marine environment (Figure 1). The system should be able to follow, identify and investigate the behavior of microorganisms in situ and in real time.

Figure 1: (center) Schematic of autonomous, coordinated network of mobile sensors. (upper left) Testing of wireless communication between nodes in tank testbed. (upper right) Autonomous, mobile node equipped with computer-controlled mobility, communications, sampling system, and Turner Designs Cyclops-7 fluorometer. (center bottom) Submersible node to be used as a data mule or for obtaining vertical profiles.

Approach:
We are studying the dynamics of blooms of the alga Aureococcus anophagefferens in the waters off Long Island, NY. Existing monitoring efforts are time-consuming and involve manual sampling and analysis. We are constructing a network of sensors and samplers, consisting of both stationary and mobile “nodes,” to allow for spatially- and temporally-rigorous monitoring and adaptive sampling. For example, changes in temperature or chlorophyll fluorescence can serve as triggers for sampling (Figure 2).

Figure 2: Concentration of Aureococcus anophagefferens (BT) and temperature with depth in a column testbed. Note the decrease in BT concentration (black profile) around the point of the thermocline (gray profile).

The stationary nodes consist of temperature and salinity sensors, Turner Designs Cyclops-7 chlorophyll a fluorometers, and associated processors and communications equipment (Figure 3).

Figure 3: Schematic of stationary node components.

These environmental sensors measure at a high frequency and signal bloom events (e.g. elevated chlorophyll levels). We are then be able to deploy the more complex mobile node (Figure 4) to make more sophisticated measurements and retrieve relevant samples.

Figure 4: Mobile node equipped with wireless communication, computer-controlled mobility and navigation, sampling system, and Turner Designs Cyclops-7 fluorometer.

The Turner Designs Cyclops-7 chlorophyll fluorometer is an integral part of the network of sensors. As a proxy for photosynthetic biomass, chlorophyll measurement is one of the most biologically-significant parameters to measure in marine systems. Previous blooms of A. anophagefferens have shown chlorophyll a levels between 5 and 50 ìg/L, although higher values are possible. We chose to use the Turner Designs Cyclops-7 fluorometer because of its flexible sensitivity ranges, low power requirements and small size.

Further information:
For additional information on this project, please contact:

Beth Stauffer
Research Lab Technician
Dept of Biological Sciences
University of Southern California
Phone: (213) 821-2123
E-mail: stauffer@usc.edu
URL: www.usc.edu

Or:

Carl Oberg
Engineering Technician
University of Southern California
Computer Science
SAL 206
941 West 37th Place
Los Angeles, California 90089-0781
Phone: (213) 740-0541
E-mail: oberg@usc.edu

Bacterial Source Tracking in Puerto Rico with Turner Fluorometers

This January we brought two Turner 10-AU field fluorometers to southwestern Puerto Rico to see how well they worked for bacterial source tracking. Bacterial source tracking tries to identify sources of fecal contamination using a variety of phenotypic, genotypic, and chemical methods. We wanted to use the fluorometers to detect optical brighteners- the colorless, fluorescent dyes in laundry detergents that make clothing "whiter than white." Because laundry detergent residues are often associated with human sewage, the combination of high fecal bacterial counts and the presence of optical brighteners in surface waters suggests that human fecal contamination is present (Table 1)

Bacterial Count		Optical Brightener		Likely Result
High		High		Malfunctioning septic system or leaking sewer pipe
High			Low	Non-human warm-blooded animals
	Low	High		Gray water in storm water system
	Low		Low	No evidence of fecal contamination at the time

Table 1. Four possible outcomes when fluorometry for optical brighteners is combined with counts of fecal indicator bacteria.

To detect human fecal contamination, we combined field fluorometry with targeted sampling for Escherichia coli, a bacterium widely used as an indicator of fecal contamination. Targeted sampling is much like the children's game of "hot and cold," and requires sampling and resampling for fecal bacteria until a persistent source of the bacteria is identified (Kuntz et al., 2003). We used the IDEXX Colilert system to identify high numbers of E. coli.

This was our first study to combine fluorometry and targeted sampling beyond our preliminary work on the Georgia coast (Gates et al., 2004). Overall, the system seemed to work well. For example, we observed high counts of E. coli and high fluorometric signals in the Yaguez River, which flows through the city of Mayagüez. We are confirming these data with PCR analysis for the presence of human virulence factor. The clear waters in Puerto Rico were an ideal testing ground for fluorometry because organic matter didn't interfere with the fluorometric signal. We are continuing to develop the combination of fluorometry and targeted sampling for Georgia waters, where high amounts of organic matter in the water do interfere with the fluorometric signal. However, for the moment, the data are encouraging for places like Puerto Rico.

References:
Kuntz, R. L., P. G. Hartel, D. G. Godfrey, J. L. McDonald, K. W. Gates, and W. I. Segars. 2003. Targeted sampling protocol with Enterococcus faecalis for bacterial source tracking. J. Environ. Qual. 32:2311-2318.

Gates, P., P. Hartel, K. Payne, J. McDonald, K. Austin, K. Rodgers, J. Fisher, S.N.J. Hemmings, and L. Gentit. 2004. Combining targeted sampling and bacterial source tracking to determine sources of fecal contamination to the south beach of Sea Island during calm and stormy conditions. Sea Island Company. 12 p.

Cornell Researchers Use Aquafluor Fluorometer To Measure Ammonia Excretion By Tropical Fish

Pete McIntyre, a researcher at Cornell University, selected a Turner Designs Aquafluor fluorometer to measure ammonia in water as part of a research project investigating the impacts tropical freshwater fish have on nutrient cycling in their ecosystem.

Application Introduction
Tropical fishes are renowned for their species diversity, interesting behaviors, and beautiful coloration. Most people associate tropical fish primarily with coral reefs, but species inhabiting tropical freshwaters account for 20-25% of the world’s total fish species diversity! Despite their impressive diversity, scientists are only beginning to understand the ways in which these fishes affect the functioning of tropical freshwater ecosystems.

There is a growing list of threats to tropical freshwater fish diversity, including overfishing, habitat degradation, introduced species, and river impoundments. At the same time, the number of humans dependent upon the rich fisheries of tropical rivers and lakes grows every year. These shifts raise critical question about whether every species plays a unique role in its ecosystem, or instead most species are equivalent in their functional roles.

Application Objectives
Pete McIntyre’s research addresses the functional contributions of tropical fishes to their ecosystems through nutrient recycling. Biologists have long recognized that animals are not very efficient at retaining the nutrients in their food, and some of these nutrients are returned to the environment in forms that are readily available to fuel new productivity of plants. In the case of fishes, most species excrete a substantial proportion of their dietary nitrogen as ammonia (NH3) that is released continuously across the gills. In ecosystems where nitrogen availability limits the productivity of algae, the recycling of dietary nitrogen by fishes could be a critical part of the nutrient cycle.

Application Results
In collaboration with Alex Flecker (Cornell University) and Mike Vanni (Miami University, Ohio), he studied the excretion of NH3 and dissolved phosphorus by fishes in a piedmont river in Venezuela. This site is home to around 80 species of fishes, including a variety of catfishes and tetras. They are investigating the determinants of nitrogen and phosphorus recycling rates, including species identity, body size, body composition, and diet. Their work has revealed great variation among species, much of which is explained by body size and composition (see Vanni et al. 2002. Ecology Letters 5: 285-293).

Their field site is not linked into a power grid, so they have always had to rely on portable field equipment that requires little power. For the last two years, they have been using a Turner Designs Aquafluor handheld fluorometer to obtain high-resolution NH3-N data in the field using only battery power. Using the OPA detection method developed by Holmes et al (1999), they have been very pleased with the instrument’s precision and linearity up to ~90 µg N/L when checked against a Turner 10-AU or autoanalyzer. Others in their research team have been equally pleased with the accuracy of low-level measurements (1-8 µg NH3-N/L) taken with the Aquafluor. The Aquafluor’s portability for air-travel and battery power for fieldwork made it a critical part of his research in South America and Africa.

They have now expanded their Venezuelan project to measure NH4 recycling by almost 50 species of fishes, and the results indicate that fishes play a critical role in quickly regenerating nutrients in this N-limited ecosystem. This information is now being combined with surveys of the fish community to determine the importance of individual species in the ecosystem.

We collect fish from riffles by stirring the rocks under which they hide in Rio Las Marias, Venezuela. By exhaustively collecting from many such quadrats, we can estimate the typical density of benthic fishes in the river.

Dozens of species of fish live in small riffles like this one. Some species feed on algae growing on the rocks, others eat the riparian vegetation, and many hunt for insects and crustaceans.

We catch fish from the river and incubate them in bags of water to measure their nutrient excretion.

For further information, please visit:
http://www.eeb.cornell.edu/flecker/flecker.html
http://www.eeb.cornell.edu/

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